Background Chlamydia trachomatis is the most prevalent bacterial sexually transmitted infection worldwide. A strong link between serogroup/serovar and serological response has been suggested previously. This study aims to elucidate serovar specific serological responses in two independent Dutch patient groups using two serological assays.

Methods We performed genotyping of serovars in two patient groups of C. trachomatis infected patients (total n = 718). We pooled the two study populations to form one study group and within this group we analysed men and women separately. We used two commercially available ELISA kits (medac Diagnostika) to determine specific serum IgG levels.

Results Calculations of the kits to determine IgG concentrations were comparable and could therefore be pooled. We observed very significant differences when comparing the mean IgG titres of three serogroups, B, C, and I. In the female group B vs. C: p < 0.0001 (mean titres B 270.0 vs. C 88.8); B vs. I: p < 0.0001 (270.0 vs. 108.5). Male group B vs. C: p = 0.0005 (190.2 vs. 69.6); B vs. I: p = 0.0002 (190.2 vs. 92.9); C vs. I was not significant. Serovars D and E of serogroup B induce the highest mean IgG titres compared to the other serovars in both men and women: 145.5 and 199.1 vs. ≤ 107.9 for men and 305.6 and 262.7 vs. ≤ 161.5 for women.

Conclusions This study shows a statistically significant higher serological response induced by B group serovars compared to the C and I group serovars in vivo in both men and women. This study is currently being extended with a different ethnical population and a different serological test.